The ability to navigate a mobile unit in a specific navigation environment is a frequently encountered technical problem. Typical examples include the navigation of transport units, robots or the like in warehouses and logistics centers, but also destination guidance of motor vehicles, for example in a parking lot or parking structure. This question becomes interesting, especially in the field of motor vehicles, if a fully automated vehicle system is provided which completely takes over vehicle guidance, thus allowing autonomous (fully automated) operation of the motor vehicle.
But even if a motor vehicle is at least partially manually operated, hints are often desired, for example in parking environments, for example for guidance to a free parking spot.
Where mobile devices are used as mobile units, such position sensing approaches are pursued in the field of “augmented reality” (AR). In this context, AR markers have been proposed for camera-based localization, said markers being optical conspicuity markings which have to comply with specific requirements such as shape, color, figure and the like. It has been demonstrated for these AR markers that relative position determination is possible down to the subpixel level. An example of such AR markers (augmented reality markers) is the “ARToolkit” by the Human Interface Technology Laboratory of the University of Washington.
Today's state-of-the-art methods of position determination are based on global navigation satellite systems (GNSS), such as GPS (Global Positioning System). However, such global navigation satellite systems can mostly be used outdoors only since reception inside buildings is difficult or impossible to achieve. Other positioning approaches, which can also be used inside buildings, are based on radio signals. Examples include so-called runtime methods and methods based on received signal strength. This however requires the rather complex installation of the suitable technical devices within the navigation environment, e.g. a parking structure.
Technologies based on optical position determination using markers are in principle much easier to implement—when using AR markers, for example, it is sufficient to install just these to at least be able to determine a relative position. Like with other markers, this is done using image processing algorithms which can derive a relative position that also includes a distance based on the way in which the marker is represented in the sensor data, e.g. a camera image, and with knowledge of the actual geometry of the marker, wherein quite frequently the properties of the respective surroundings sensor must also be known to be able to determine a distance. These image processing algorithms have to process an extremely large amount of data in order to at least partially detect and identify the markers, which can be rather small in the sensor data, particularly if a robust operation has to be ensured. This results in a calculation effort that entails high costs and is generally rather undesirable. Another problem of using dedicated optical markers is that these markers first have to be manufactured/installed.
It should be noted here that, when talking about a “position” of the mobile unit in this description, this typically includes an orientation of the mobile unit in addition to an indication of its place, since this is frequently needed, particularly for navigation applications.
While a relative position applies only in relation to the optical marker, an absolute position for the navigation environment makes it possible to simply locate the mobile unit on a map of the navigation environment in a system of coordinates that at least applies to said environment and to relate it to other features of the navigation environment.
WO 2009/098319 A2 relates to a navigation device for a motor vehicle. It uses position markers at fixed positions along a highway, wherein images from a camera that record a scene in front of the motor vehicle are evaluated to identify position markers, whereafter an absolute position of the position marker is determined using information assigned to said marker, and furthermore a distance between the motor vehicle and the position marker is determined by image processing and an estimation of the position of the motor vehicle is determined from said absolute position and said distance. The markers themselves may contain information about their position or information from which their position can be determined, wherein said position information of the position markers can be retrieved from a memory.
DE 10 2009 045 326 A1 relates to a method and system for designing a database for determining the position of a vehicle using natural landmarks. The object is to record images of the surroundings of the vehicle in a preset route section before reaching a danger point, to determine at least two natural landmarks from the images of the surroundings, to detect reaching of the danger point, and, upon reaching the danger point, to store at least two of the determined landmarks as well as the respective associated vehicle position at the time when the respective image of the surroundings was recorded. The idea is to determine the position relative to a danger point using landmarks if position determination using a conventional positioning system is not sufficient. It is conceivable that video sensing and/or the calculation unit are only activated within the route section before reaching a danger point, wherein then images of the surroundings are recorded and landmarks are determined and stored, where required.
DE 41 38 270 A1 relates to a method for navigating a self-propelled land vehicle, wherein markers are detected as the vehicle travels, digitized and compared with stored data to determine deviations from desired values which are processed into navigation interference signals, wherein said stored data are generated during a learning journey. The idea is to use natural landmarks located in the area. A video camera that can be pivoted about an axis vertical to and about an axis horizontal to the plane of travel, which video camera is to record the landmarks, such that it is eventually possible to calculate the current position of the vehicle relative to a desired point and the current direction of the vehicle with respect to a desired direction. Stored landmarks are used to aim the camera at various landmarks one after the other. The travel time associated with the route must be long enough for this, however.
DE 10 2011 112 404 A1 relates to a method for determining the position of a motor vehicle, which also uses markers, in this case objects, and substantially discloses a procedure in accordance with the introductory part of claim 1. The position determined using the satellite positioning system can also be used to identify the object.
DE 101 21 260 A1 relates to a navigation system as expansion for satellite navigation devices in “indoor range”, wherein a parking spot of the motor vehicle can for example stored on a “car finder key”.